Electro-osmotic pumps for drug release were considered since 1977 when Luft, Kuehl, and Richter (LKR) working at the Siemens Research Laboratory in Erlangen reported an electro-osmotic-pump-based insulin delivering system designed for long-term implantation in diabetic people. To avoid passage of the insulin through the pump, which would have fouled the pump, saline water was pumped. The saline water solution pushed a mobile separator, which, in turn, drove the insulin solution. The LKR pump was elegant in its simplicity, comprising merely an ion-exchange membrane sandwiched between two electrodes. It had no moving parts and its flow rate was current-controlled. Although the LKR pump was considered for use in insulin delivery, it has yet to reach the diabetic people for whom it was intended.
Electro-osmotic pumps have found applications in compact bioanalytical systems and in heat pumps. In some of these, the pumps now drive liquids through long and narrow long on-chip and off-chip capillaries and through miniature packed chromatographic columns Pumps have been integrated in silicon chips and are part of lab-on-chip devices. While polymeric ion exchange membranes were used in the early pumps, the more recent pumps have ceramic membranes, particularly of porous silica, although porous silicon and aluminum oxide have also been used. Platinum electrodes, on which water is electrolyzed at the applied high voltages ranging from 3V to 400V are usually used. Gas bubbles resulting from electrolysis, however, may interfere with the operation of the pumps Electro-osmotic pumps having ceramic membranes and gas-evolving electrodes are now sold, for example, by NFT (Nano Fusion Technologies, Tokyo).